You can use Wireshark to display the content of UDP packets.
To do this append -Tfields -e data to the wireshark command.
E.g. sudo tshark -f "port not 53 and not arp and not tcp and not stp and not icmp6" -i enp65s0f0np0 -Tfields -e data
Disclaimer: This is something I just learned so I might be completely wrong. If I am please let me know, my email is in the footer.